It is often desirable to increase the fracture surface area within a geothermal reservoir or within an Engineered Geothermal System because increases in surface area can be equated to increased rates of energy extraction. The conventional method of increasing surface area is through a hydraulic stimulation procedure wherein large volumes of water are injected at moderate flow rates over several days. Currently, effectiveness of the stimulation procedure is determined by measuring and correlating decreases in pressure as a result of pumping. For example, for a given flow rate, a wellhead pressure drop can be assumed to correlate with an increase in injectivity due to an increase in the number and/or size of fractures. Subsequent pressure, temperature, and/or spinner logging can help to quantify the creation of new fractures.